MOLECULAR-DYNAMICS SIMULATION WITH AN AB-INITIO POTENTIAL-ENERGY FUNCTION AND FINITE-ELEMENT INTERPOLATION - THE PHOTOISOMERIZATION OF CIS-STILBENE IN SOLUTION

An interpolation scheme for potential energy surfaces is presented. It employs a regular grid and finite element interpolation. The aim is t he reduction of the computational expense for molecular dynamics simul ation with a quantum chemical potential energy function. The methods u sed are described in detail. The feasibility is demonstrated and the e fficiency and accuracy are evaluated for the photoisomerization of cis -stilbene in supercritical argon, using an ab initio configuration-int eraction treatment for the first electronically excited state of the s tilbene molecule and classical force fields for the solvent-solute int eractions (quantum mechanical/molecular mechanical molecular dynamics) . The number of required quantum chemical calculations of energy and g radients was substantially reduced compared to a simulation not using the interpolation scheme. On the other hand, the impact on the accurac y is insignificant. (C) 1998 American Institute of Physics. [S0021-960 6(98)51321-9]